The present invention relates to the technological field of optical apparatus and, particularly, to an optical apparatus combined with a mechanical scanning device for measuring the depth of grooves forming fine circuit patterns on a semiconductor substrate.
In pursuit of more highly integrated semiconductor devices, the semiconductor circuit design is coming to a turning point from the conventional planar device structure to a cubical device structure. On this account, the technique of measuring the depth of etched grooves in a semiconductor substrate becomes indispesnsable. Such etched grooves are designed to have a depth of 3-5 .mu.m and a width of 1-2 .mu.m, but it is not easy to measure the actual etch depth. The following are publications disclosing techniques of measuring the depth or thickness of a fine structure.